Strain Improvement of Micro-organisms Used in fermentation.
In industries the micro-organism are selected by using various screening procedure.The strain which is selected on industrial scale for commercial production of a product should be able to produce high yield of product constantly.This constant high yield of product makes the fermentation economic as well as face the competition with other industries.For obtaining high yield of product the industries carry out strain improvement as well as strain selection programs continuously. During the strain improvement program various parameters are adjusted to increase product yield.
The parameters like pH,temperature,media components,aeration,agitation,innoculum levels are adjusted and variation in this levels are tested for increasing yield of product.But however this change in parameters doesn’t give large yield and effective results by microbial strains used. The fermentation organism which is being used in fermentation can give constantly increased high yield of product by use of strain improvement program and selection of the most efficient strain for production of product on industrial scale.
The strain improvement of micro-organism used in fermentation process is done by altering the genetic make up of strain and selecting the most efficient strain from various improved strain and result in increased yield of product.After the strain improvement program the selected strain should be genetically stable.The selected strain should produce desirable product in large amount and undesired product in less quantity.Before caring out the mutation program the selected strain should be efficient under all optimum fermentation condition.The selected strain is exposed to various strain improvement programs and the strain giving high yield of product is selected among all tested strains.The strain that is selected should be able to produce high amount of yield as compared to the original unaltered parent strain.
The genetic make-up of selected strain can be changed by using following methods:-
- Genetic recombination or gen transfer.
- Genetic engineering
1] Genetic recombination or gen transfer
The genetic recombination mechanism exist in different strains of bacteria and some actinomycetes. In genetic recombination mechanism transfer of a gene from one type of strain to other type of strain of micro-organism takes place.This gene transfer takes place by conjugation,transformation or transduction. Gene transfer can be carried out by protoplast fusion of two different efficient strains and new improved strain can be developed.
The fungal strain undergo para sexual cycle and mitotic cell division which is very important and of great value in strain improvement.Genetic Breeding is also possible in different genera of yeast.Thus by using genetic recombination and gene transfer technique it is possible to combine the desired characters from two different strains of same species by interstrain breeding and obtain a efficient strain that is able to produce high yield of product on industrial scale.
Mutation can be defined as change in genetic structure of micro-organism.The ability of micro-organism to produce a desired product can be enhanced by a mutation process.In mutation process the most stable and efficient strains are exposed to mutagenesis by using different mutagenic agents.The mutagenic agents like ionization,ultraviolet radiation,acids,and alkalies are used in mutation.Result of mutation obtain should be increased in yield of desired product and decreased yield of undesired product.The mutagenic agents are used in such concentration that maximum number of cells die due to mutagenic agents and only the that are capable to carry out mutation and have the capacity to tolerate the levels of mutagenic agents are able to survive.From the survived cells the cells which are undergone mutation and have the capacity to produce high yield of fermented product is selected.
The selection of a mutated cell is a very difficult task. Whenever the microbial cells are subjected to mutation their are two possibilities and that are the mutation occurred may be major mutation or minor mutation. The strain undergone desired mutation should be carefully selected,isolated and maintained properly.The selected mutant strains with altered morphological and biochemical characters are now the strain that produce high yield of desired product.The improved selected strain should be tested with laboratory scale experiments followed by pilot plant experiments and then further used on commercial scale.The finalized strains are selected,purified and maintained.All the test and experiments should be carried out with high accuracy as these procedures are time consuming and expensive.Further when these strains are used on industrial scale a proper record of yield produce should be maintained as minor changes should be noted.
3] Genetic engineering
Genetic engineering technique is the most successful technique used for strain improvement programs on industrial scale.It is also called as Recombinant DNA technology and in this process their is alteration of genetic characters of cells and hence result in change in phenotypic character of cell.This In this technique a desired type of gene is introduced from one microbial cell to other microbial cells by using cloning vectors,like plasmids ,phages or cloning vectors.A specific and desired character of a microbial cells can be introduced in the selected strain to improve the yield of product.